Means for eliminating static and other distrurbances



Jan. 28, v 1936. MURRAY 2,028,841

MEANS FOR ELIMINATING STATIC AND OTHER DISTURBANCES Filed Jan. 17, 1934 2 Sheets-Sheet 1 Y S] C G1, I

52y 4 recea/er rm Gnd coal/fad mllllllm fnvenfor.

Allbrnga',

Jan. 28, 1936. c. MURRA'Y 2,028,841

MEANS FOR ELIMINATING STATIC AND OTHER DISTURBANCES Filed Jan. 17, 1954 2 Sheets-Sheet 2 ('2 I as P2 I I P A rubez Tubel A DU Tube3 mmnm + 061 v: 062 R.P1

+CG 1/7111 2 V.D.P3

Patented Jan. 28, 1936 UNITED STATES PATENT OFFICE MEANS FOR. ELIMINATING STATIC AND OTHER DISTURBANCES 3 Claims.

My invention has for its principal object the elimination or reduction to a minimum of the effects of electrical disturbances such as static, so as to prevent such disturbances from being reproduced in the loud speaker or reproducing device of such apparatus.

My invention involves the use of thermionic vacuum tube elements and electric circuits so arranged and connected as to reverse the phase of the static impulses in one circuit thereby causing the original static impulses in another circuit to be substantially cancelled out of the reproducing device.

A preferred arrangement of apparatus, and method of operation are described in the following specification and illustrated in the accompanying drawings.

In the drawings:

Fig. 1 is a diagram of the circuits and apparatus as used with a radio receiving set;

Fig. 2 is a simplified diagram showing the relation of the static receiver to the static neutralizing control grid of the radio receiver; and

Fig. 3 is a group of graphs showing simultaneous voltages of the tube elements.

Referring to the drawings in detail, SI indicates a primary signal receiver and volume control unit of any known or other suitable form having the usual tuning and volume control means, connected through tube I and transformer T to a suitable signal receiving or reproducing device S3. The element S2 is a static receiver which may be of any known or other suitable form of radio receiver and volume control preferably substantially like the receiver unit SI, but with its output connected to a relay tube, designated tube 2, for controlling current flow through a resistance tube designated tube 3. The output or plate element P2 of tube 2 and the input or cathode-grid circuit of tube 3 are connected together and are connected also to a neutralizing grid CG2 in the primary relay tube l. Other apparatus elements and their cooperative relation with each other will be described in the course of the description of operation which follows.

In operation, the desired signal, together with the static impulses are received and regulated in the apparatus SI, the output of which is connected to the grid CGI in tube I.

The electrical disturbances or static impulses alone, are received and regulated as to volume in the apparatus S2, the output being connected to the grid CG in tube 2. This circuit may be tuned to a desired frequency or it may be adjusted to a particular frequency band, which tuning or adjustment must not be the same as that of Si or the desired signal will be cancelled out.

It will be noted that both grids CG and CGI receive the same static impulses at the same time and at a desired strength, the output volume controls in SI and S2 being suitably adjusted to this end.

The electronic action in the tubes 2 and 3,. are as indicated in Fig. 3. These curves are all based on time, with the horizontal center line representing zero charge or no signal on the grids CG and CGI. The shaded portion of the curves represent the actual voltage or resistance change due to the change in charge on the control grids CG and CGI.

The element CG in tube 2, receiving a positive charge, lowers the electrical resistance between C2 and P2, thus lowering the voltage between these two elements as indicated at V.D. P2 (Fig. 3), and the potential difference between the elements C3 and P3 in tube 3 will automatically rise, taking up most of, this difference.

When a negative impulse energizes the same element CG in tube 2, the electrical resistance between C2 and P2 will increase and the voltage across these two elements will automatically rise and the voltage drop between the elements C3 and P3 in tube 3 will simultaneously decrease.

In Fig. 2, the grid CGZ in tube I, being electrically connected to the junction point between the tubes 2' and 3, will receive the same change in voltage as that across C2 and P2, or between P2 and ground.

In Fig. 3, a positive charge on both grids CG and CGI has the effect of lowering the internal resistance of the, tubes l and 2, with a resultant lowering in voltage at P2. This lowers the voltage of grid CGZ which will counteract the effect that CG! would have had if 0G2 had been held at a constant voltage.

The reverse effect holds true with a negative charge on the grids CG and CGI, in which case the voltage at CG2 being raised, the effect of that portion of the negative charge on the grid CGI due to static is thereby cancelled.

The voltage charge due to static on CGZ being degrees out of phase with the charge due to static on the grid CGI, the plate current will remain substantially unchanged by the static as indicated in Fig. 3 at RPI The tube 3 must act as a pure electrical resistance with low electrical capacity and practically no time lag, as the voltage change across this unit must keep in synchronism with the vari- 'ations in plate resistance of tube 2 in order to keep the static impulses in P2 at 180 degrees out of phase with the original static impulses charging CGI. The internal resistance of tube 3 is regulated by a suitable biasing resistance RI. This tube may be enclosed in the same envelope with tube 2, and may be inthe form of a simple rectifier having the proper characteristics to match the required voltages and currents of the other tubes in the circuit. 7

While the means, constituting the present invention, for eliminating static and other disturb ances from electrical receiving systems have been described herein in connection only with a radio receiving set, it is obvious that said means can 'be used, when suitably modified as well understood by those skilled in the art, in connection with other receiving systems.

What is claimed is:--

l. In an electrical signal receiving system comprising several thermionic relays and a thermionic resistance tube, the method of separating undesired electrical variations from desired electrical variations which comprises impressing the combined undesi'redand desired variations on a control grid of one or 'said thermionic relays, impressing the undesired variations on the control grid of the second thermionic relay to vary the currentfiowing through said thermionic -resistance tube thereby producing voltage variations between the two latter tubes corresponding to the undesired variations but in opposite phase, and impressing said voltage variations on a control grid in said first-mentioned thermionic relay.

2. A radio receiving system comprising :a remerit orthe second relay.

ceiver, a second receiver, a signal reproducer, a thermionic relay having a pair of grids arranged to receive voltage variations on one of said grids from said first receiver and having its output circuit connected to the signal reproducer, a re sistance tube arranged to act as a substantially pure electrical resistance with low electrical capacity and substantially no time lag, a second relay tube connecting the output of said second receiver to said resistance tube, the other grid of said thermionic relay tube being connected to a point between the resistance tube and the second relay tube.

3. In an electrical signal receiving system, means for separating undesired electrical oscillations from desired electrical oscillations comprising a receiving unit tuned to the frequency. of the desired oscillations, a thermionic relay having a cathode, two grids and a plate, the cathode and one grid being connected to the output circonnected in series in the output circuit of said second relay and having substantially no 19160- tric'al capacity or time" lag, the othergrid o'fsai'd first named thermionic relay being connected to a point in the output circuit "01' the second relay between the resistance device and the anode ele- MURRAY.

vso 

